What was found
DURING CLIMB, THE FIRST OFFICER NOTICED THE CABIN PRESSURE CLIMBING, SWITCHED TO MANUAL CONTROL, AND LEVELED OFF AT FL 228. STARTED QRH MEMORY ITEMS FOR RAPID DEPRESSURE, NO EICAS MESSAGES NOTED. INITIATED RAPID DEPRESSURE PROCEEDURE, DUE TO PUTTING CONTROL IN MANUAL AND CABIN ALTITUDE. R & R THE MANUAL CONTROLLER IAW AMM 21-31-02. OPS CHECKED GOOD.